Solicitors need to verify where your money is coming from because it is an essential aspect of client due diligence.
They do this to ensure that your money does not come from any criminal activities and that you are not using the firm as a vehicle to clean that money for instance.
For example, if you purchase a house, a conveyancer has to comply with anti-money laundering regulations and verify where the funds you are using to buy the property are coming from. To do that, they must also ensure that your financial situation is consistent with the property’s value. Law firms do this because it is their legal duty under Regulations 27 and 28 of The Money Laundering, Terrorist Financing and Transfer of Funds Regulations 2017.
By doing this, they aim to prevent criminals from potentially using law firms to launder money.